The maximum value of resistance which, when placed across the rails at
the relayAn electro-mechanical switching device used in many types of Signalling Systems. More end of a Track CircuitAn electrical device using the rails in an electric circuit, which detects the absence of trains on a defined section of line. More will cause the RelayAn electro-mechanical switching device used in many types of Signalling Systems. More to de-energise (that is,
just break its front contacts).